Regression in distributing on conditional types with T extends T after updating to 5.4 #57736
Description
🔎 Search Terms
"conditional", "distributive", "distribution"
🕗 Version & Regression Information
- This changed between versions 5.3 and 5.4
⏯ Playground Link
💻 Code
type obj = {
foo: 1;
bar: 2;
};
type keyContaining1<
str extends string,
keys extends keyof obj = keyof obj,
> = keys extends infer key extends keyof obj
? key extends `${string}${str}${string}`
? obj[key]
: never
: never;
type _1 = keyContaining1<"foo">;
// ^? type _1 = 4
type keyContaining2<
str extends string,
keys extends keyof obj = keyof obj,
> = keys extends keys
? keys extends `${string}${str}${string}`
? obj[keys]
: never
: never;
type _2 = keyContaining2<"foo">;
// ^? type _1 = never🙁 Actual behavior
The value of the generic param collapses to never when an additional conditional is added after the distributive conditional.
The error happens only when distributing with T extends T.
T extends any, T extends unknown, T extends infer U works fine.
🙂 Expected behavior
That the distributive type works similarly to the previous versions.
Additional information about the issue
No response